Powercap_rapl sensor

Pre-requesites

At the time those lines are written, this sensor works only on:

OS: GNU/Linux
Intel and AMD x86 CPUs, produced after 2012 (or some laptop cpu prior to 2012)

It needs the following kernel modules to be present and running:

On kernels 5.0 or later: intel_rapl_common

On kernel prior 5.0: intel_rapl

For AMD processors, it seems that powercap/rapl will work only since kernel 5.8 and 5.11 for family 19h.

Energy consumption data can be directly collected on a physical machine only.

To collect energy consumption on a virtual machine, you may first collect power consumption data from the hypervisor thanks to the qemu exporter and then collect those metrics in the virtual machine thanks to this sensor, with --vm flag enabled.

Usage

To explicitely call the powercap_rapl sensor from the command line use:

scaphandre -s powercap_rapl EXPORTER # EXPORTER being the exporter name you want to use

You can see arguments available from the cli for this sensors with:

scaphandre -s powercap_rapl -h

If running in a virtual machine:

scaphandre --vm -s powercap_rapl EXPORTER

Please refer to doc.rs code documentation for more details.

Options available

sensor-buffer-per-socket-max-kB: Maximum memory size allowed, in KiloBytes, for storing energy consumption for each socket
sensor-buffer-per-domain-max-kB: Maximum memory size allowed, in KiloBytes, for storing energy consumption for each domain

Environment variables

If in --vm mode, you want to read metrics from another path than the default /var/scaphandre, set env var SCAPHANDRE_POWERCAP_PATH with the desired path.

Troubleshooting

When running scaphandre on Ubuntu 20.xx I get a `permission denied` error

Since linux kernel package 5.4.0-53.59 in debian/ubuntu, powercap attributes are only accessible by root:

linux (5.4.0-53.59) focal; urgency=medium

  * CVE-2020-8694
    - powercap: make attributes only readable by root

Therefor, the user running scaphandre needs to have read access to energy_uj files in /sys/class/powercap.

You can run the init.sh script to apply appropriate permissions to the required files.

Scaphandre documentation